Building organisms

Every living animal and plant starts its life as a single cell. The cell then divides many times, and the end result is a fully functioning organism, like a rose bush or a horsefly or you or Brian Blessed. A human is made of quadrillions of cells, but they all come from that one initial fertilized egg. All (or at least most) of the information that makes you you can be compacted town to one nucleus of one single cell, and then read out in such a way that when that one cell starts to divide quadrillions of times, the new cells congeal into an all-signing, all-dancing organism-y thing. I think this is pretty awesome, and thinking about these problems has led me to working on a PhD studying Heliconius butterflies. This post is a personal perspective on this problem and how I came to study butterflies.Joe Hanly….or Henry Walter Bates?

The processes that make an animal from a single egg are controlled in such a way that they will always make a pretty accurate version of that animal. This process is really repeatable. Hold your hands together. They’re pretty much exactly the same size and shape, correct? In fact, I’d hazard a guess that your hands are more or less the same shape as the hands of all the other humans you know, too. All of the hands of all humans, including your own two hands, were put together completely independently of each other, yet in most cases they are pretty much perfectly formed (apologies to readers with polysyndactly. And to amputees).

How does that work? How does a hand come to be a hand, and what are the physical mechanisms that can build hands so perfectly and repeatably? How about feet, how do they happen – I guess in a similar way to hands, but with some differences? How does one make a face? I be that’s probably pretty different from the way you make a hand, right? Lungs? Wings? Shells? Roots? I’ve always wondered about how all this stuff gets put together from one egg. I always enjoyed learning about science at school, and studied Biology, Chemistry, Maths and History for my A-levels, and so when I was 17 and I actually had to start deciding what I wanted to do with my life, I decided to go and do a course in Developmental Biology at the University of Manchester.

While I was there, I actually learnt about how hands and faces and lungs and other bits develop, and why we think the process is so symmetrically perfect and repeatable. I’m not going to talk about that here (if you’re interested in these things, then I’ve put some useful links below), but while I was learning about this, I started realise there were even more questions I hadn’t really even considered before.

Firstly, I got really interested in gene regulation. For living things to function, they need to make proteins from genes. While some of these proteins need to be present in all places at all times (for example, the genes important for respiration) others need to be turned on or off in specific places and at specific times, for example, the proteins that make melanin pigments, or the proteins that form the structure of bone. If the proteins that make bones were present everywhere throughout your body, you’d be in trouble. It turns out that while we know quite a bit about the process of turning genes on and off, there is still a lot to be found.

I also got really interested in the way that gene regulation can relate to evolution. Over time, the physical form that a species develops will change in response to selection. Sometimes, these changes might involve the evolution of entirely new proteins or changes to existing proteins, but it turns out that the simplest and most common change that leads to differences in morphology actually affect the ways that genes are turned on and off.

When I finished my degree I decided that I wanted to continue studying science, so I applied for funding for a PhD from the Wellcome Trust, and came to study at the University of Cambridge. I’m working on Heliconius because it turns out to be a good system for investigating how differences in gene regulation can evolve, as we have one species with many different pattern forms, and we can use these patterns to gain an understanding of how the genetics which control phenotypic differences work. I’ll talk more about this in another post, though.

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